Mavericks fire multiple staffers, including head athletic trainer, after internal conflict

Dallas Mavericks general manager Nico Harrison dismissed head athletic trainer Dionne Calhoun and athletic performance director Keith Belton on Wednesday, along with several other employees, sources confirm, as first reported by DLLS’ Marc Stein, continuing his thorough rebuild of many basketball-facing employees who had been with the team prior to Harrison’s appointment in 2021. Calhoun, specifically, had spent 21 season with the organization and had been promoted to head athletic trainer in 2019.

Belton, on the other hand, was appointed just last season after Dallas’ longtime trainer, Casey Smith, was fired in August 2023. There had been internal tension this past season between him and first-year director of health and performance Johann Bilsborough, who sources say will retain his role, most notably involving the health of second-year center Dereck Lively II. On April 21, DLLS was the first to report details of the “notable blowup” between them.

As reported then: “The issue, multiple team and league sources say, stemmed from a difference of opinions regarding (Lively’s) health, with Belton thoroughly preparing Lively to return to play before a January game before Bilsborough pushed back. Bilsborough and Belton share an office in the training room of the team’s practice facility, and the issue sparked soon after when Belton repeatedly interrupted a meeting that Bilsborough was finishing in that shared space. The disruption was notable enough that team leadership, and later the team’s human resources department, had to be involved.”

Lively did not play and was sent for a CT scan that revealed a stress fracture in his ankle, which kept him out for the following 36 games. It was one of several significant injuries suffered by Mavericks players during the season, which sparked questions about the training staff that Harrison had assembled. As reported in April by ESPN, Belton also lacked the certifications from the National Strength and Conditioning Association that the NBA requires for such employees with his title.

In a closed media event in April, Harrison had defended his hires when questioned about them, saying, “We feel that the guys that (have) replaced them have done an amazing job. And again, you’re coming at me from a negative standpoint, and I look at it from a positive standpoint, the guys that we brought in are better.” However, team sources said that the tension had been so inflamed between Belton and Bilsborough that it was difficult to imagine both remaining with the team following the season, which proved correct.

Harrison’s answer was in response to a question asked about training staff members who had previously been dismissed, starting with Smith, who had spent 19 seasons with the team prior to his 2023 firing. Just days after the Mavericks’ 2023-24 season ended in a Finals defeat, Harrison had also dismissed athletic performance director Jeremy Holsopple and manual therapist Casey Spangler.

Calhoun, like Holsopple and Spangler, had worked alongside Smith for years, and team sources had expected he would be vulnerable to Harrison’s continued re-envisioning of the franchise given his status as a holdover from the past regime. Now, Harrison will once again be responsible for rebuilding the team’s training staff this summer.